The subject clone is a sport of Malling 9 MM9), an unpatented apple rootstock clone. The original plant was selected as a mutation in 1967 from a large stoolbed of M9 plants. The stoolbed had been planted in 1960 and was growing in the Rene Nicolai nursery, Linderstroot, 22-B-3820 Alken, Belgium. The original source of the bed was the East Malling Research Station in England. The clone was one of a group of clones that were selected by Mr. Nicolai and other rootstock specialists for their differences in lateral branching, leaf development and shape, leaf color, thickness of the shoots, rooting ability in the stoolbed, bloom characteristics and other noticed differences from the mother stoolbed plants.
Following its selection, the clone was assigned a number (RN8) and was propagated for further testing and evaluation.
Since all original M9 rootstocks have been found to be virus infected, RN8 stocks were subsequently heat-treated by application of dry heat in order to obtain virus-free specimens. After heat treatment and subsequent virus testing, the new rootstock clone was again exposed to multiplication techniques (stooling) followed by continued testing and evaluation.
Virus-free RN8 progeny plants were expanded into small stoolbed plantings which were planted separately rately in order to examine the new rootstocks's individual characteristics in small semi-commercial stoolbed sites.
These small experimental stoolbeds of RN8 were established for such further evaluations as follows:
1. A site at Deveaux, Belgium was planted in the spring of 1974 with 555 plants of the subject clone.
2. A site at Bordeaux, France was planted in 1977 with 200 plants of the subject clone.
3. A site at Wissenhoeve, Belgium was planted in the spring of 1980 with 1,176 plants of the subject clone.
4. A site near St. Truiden, Belgium was planted in the spring of 1982 wtih 100 plants of the suject clone.
5. A site at Henkaenrts, Belgium was planted in the spring of 1986 with 4,600 plants of the subject clone.
6. A site at Ephrata, was planted in the spring of 1990 with 2,000 plants of the subject clone.
Clone RN8 was subsequently finally selected as a rootstock clone that continues to possess growth and rooting characteristics that are distinctly different from its M9 parent.
It distinguished itself in these beds from its M9 parent in the following ways:
1. The subject clone produces fewer lateral limbs (feathers) than its M9 parent. At the Bordeaux test site in France and at the Ephrata, Wash. site, feathers produced were about one half the number produced on its M9 parent (FIGS. 1 and 2; Tables 1 and 2). RN8 grows less robustly in the stoolbed and exhibits a shorter, stockier growth characteristic when compared to its M9 parent (FIG. 4, M9; and FIG. 5, RN8). Nodes are spaced closer together on shoots and average stem circumference is significantly more than the average stem Circumference of M9 (Table 2). The average length of feathers on RN8 was slightly less than the average length of feathers on its M9 parent (Table 2).
TABLE 1 ______________________________________ Percent of Layer Plants with Side Limbs (Feathers) (Test Stooling Beds at Bordeaux, France) Rootstock Year Clone 79/80 80/81 81/82 82/83 Average ______________________________________ M9 13 8 25 0 11.5 (virus-free) RN8 8 6 13 0 6.8 RN19 41 32 44 19 34.0 RN29 39 22 35 15 27.8 ______________________________________
TABLE 2 ______________________________________ Growth Characteristics (Test Stooling Beds at Ephrata, Washington) Length Number Number Length Number Circum- of of of of of ference Rootstock Shoot Nodes/ Spurs/ Spur Leaves/ of Stem Clone (cm) Shoot Shoot (cm) Shoots (cm) ______________________________________ M9 66.80* 39.20 3.00 1.50 53.00 3.24 RN8 62.10 42.10 1.80 1.20 57.20 3.80 RN19 78.20 41.00 18.60 8.60 88.30 3.51 RN29 86.20 45.60 21.40 10.30 100.00 3.54 ______________________________________ *All numbers shown are the average of 100 plants selected at random.
2. Leaves of the subject clone are larger and more rounded in shape and leaf margins are more sinuate than those of M9. Leaves of RN8 are round to oval in shape with broadly acute tips. Theis leaf characteristic is very pronounced in the older leaves (FIG. 3; Table 3).
TABLE 3 ______________________________________ Leaf Size and Respetive Petiole Length of Respective Rootstock (Test Stooling Beds at Bordeaux, France) Rootstock Length, L Width, W L + W Length of Clone (mm) (mm) (mm) Petiole ______________________________________ M9 101.7 63.8 165.5 32.5 (virus-free) RN8 98.8 73.6 172.4 34.0 RN19 91.4 60.0 151.4 30.8 RN29 85.5 57.1 142.6 28.5 ______________________________________
3. The profuse blooming characteristic of RN8 is very pronounced and in this respect differs distinctly from its M9 parent. The number of blooms produced on RN8 two-year-old line-out stocks was about two-fold that of its M9 parent (Table 4).
TABLE 4 ______________________________________ Bloom Characteristics (Research Station at Gorsum, Belgium - 1985) Rootstock % of Rootstocks With Bloom Clone (1 Year From Stoolbed) ______________________________________ RN8 29 RN19 4 RN29 0 M9 15 (virus-free) ______________________________________
4. Rooting ability (number and quantity of roots produced per length of stoolbed shank) of the subject clone is significantly more than that demonstrated strated by its M9 parent. Also, the average number of rooted plants produced per stoolbed mother plant and/or per meter of stoolbed row is significantly more than the average produced by M9 mother stocks (Table 5 , 6 and 7). This difference in number of rooted daughter plants was approximately two-fold at the test site near Bordeaux, France after five years in the stoolbed (Table 7). These characteristics are stable and have been transmitted without change through succeeding generations.
TABLE 5 ______________________________________ RN8 Stoolbed Production (Deveaux, Belgium) No. Mother Plants - 555 Length of Bed (m) - 185 ______________________________________ Year 82/83 83/84 84/85 85/86 86/87 ______________________________________ Grade (mm) 10/12 300 150 150 1,100 500 8/10 0 0 700 0 0 6/10 4,650 3,350 0 0 2,800 6/8 0 0 3,700 3,100 0 5/7 0 0 0 0 0 4/6 2,400 1,800 3,200 1,900 3,900 04 0 600 0 0 0 #2s 1,000 1,400 600 900 1,900 Totals 8,350 7,300 8,350 7,000 9,100 Per Mother Plant 15.05 13.15 15.05 12.61 16.40 Per Meter 45.14 39.46 45.14 37.84 49.19 ______________________________________ Average Year 87/88 88/89 89/90 90/91 82/91 ______________________________________ Grade (mm) 10/12 675 200 0 0 8/10 925 1,925 850 2,225 6/10 0 0 0 0 6/8 3,300 2,700 3,000 0 5/7 0 0 0 3,450 4/6 2,700 1,200 3,400 1,600 04 0 0 0 0 #2s 1,300 1,100 3,400 700 Totals 8,900 7,125 10,650 7,975 Per Mother Plant 16.04 12.84 19.19 14.37 14.96 Per Meter 48.11 38.51 57.57 43.11 44.89 ______________________________________
TABLE 6 ______________________________________ M9 (Virus-Free) Stoolbed Production (Deveaux, Belgium) No. Mother Plants - 561 Length of Bed (m) - 187 ______________________________________ Year 82/83 83/84 84/85 85/86 86/87 ______________________________________ Grade (mm) 10/12 225 100 250 750 464 8/10 0 0 450 0 0 6/10 4,150 2,950 0 2,350 2,200 6/8 0 0 3,400 0 0 5/7 0 0 0 0 0 4/6 1,800 1,600 2,200 1,600 3,000 04 0 300 0 0 0 #2s 700 800 500 500 1,400 Totals 6,875 5,750 6,800 5,200 7,064 Per Mother Plant 12.25 10.25 12.12 9.27 12.59 Per Meter 36.76 30.75 36.36 27.81 37.78 ______________________________________ Average Year 87/88 88/89 89/90 90/91 82/91 ______________________________________ Grade (mm) 10/12 75 -- -- -- 8/10 450 -- -- -- 6/10 0 -- -- -- 6/8 2,700 -- -- -- 5/7 0 -- -- -- 4/6 2,200 -- -- -- 04 0 -- -- -- #2s 400 -- -- -- Totals 5,825 -- -- -- Per Mother Plant 10.38 -- -- -- 11.14 Per Meter 31.15 -- -- -- 33.43 ______________________________________
TABLE 7 ______________________________________ Average Number of Plants Per Stoolbed Mother Plant (Test Stooling Beds at Bordeaux, France) Year Planted and Age Rootstock 79/80 80/81 81/82 82/83 Clone 2-Yr 3-Yr 4-Yr 5-Yr Average ______________________________________ M9 1.2 2.6 .5 4.0 8.3 (virus-free) RN8 2.1 3.9 3.8 6.4 16.2 RN19 2.6 4.4 6.5 9.1 22.6 RN29 4.4 5.6 5.7 11.3 27.0 ______________________________________